The subject invention relates to an apparatus and method for testing an ignition coil and a spark plug and, more particularly, to an apparatus and method capable of identifying defects in an ignition coil and a spark plug connected in a xe2x80x9ccoil on plugxe2x80x9d design.
Most conventional spark-ignition engines include a single ignition coil wired to several spark plugs for initiating fuel combustion in each engine cylinder. To ensure quality, these engines are typically cold motor tested for defects prior to shipment to a vehicle assembly plant. During the cold motor testing, each engine is mechanically cranked by an external testing mechanism through at least one complete engine cycle. Thus, there is no combustion of fuel during the cold motor testing.
To detect ignition coil and spark plug defects, conventional engine testing methods have monitored an electrical signal transmitted from a secondary side of the ignition coil to each spark plug during each spark generation. However, the recent development of a new ignition coil and spark plug packaging arrangement, commonly referred to as a xe2x80x9ccoil on plugxe2x80x9d design, has rendered such prior art testing methods obsolete.
Unlike conventional designs, the xe2x80x9ccoil on plugxe2x80x9d arrangement provides one ignition coil and one spark plug for each engine cylinder. The xe2x80x9ccoil on plugxe2x80x9d design additionally includes a boot or sleeve which extends from the secondary side of the ignition coil to the middle of the spark plug. Thus, the boot insulates the entire length of an electrical transmission wire connected between the ignition coil and the spark plug. As a result, access to the aforementioned electrical signal is not available in the xe2x80x9ccoil on plugxe2x80x9d design. Accordingly, it would be desirable to provide an apparatus and method for testing an ignition coil and a spark plug connected in a xe2x80x9ccoil on plugxe2x80x9d design.
In a disclosed embodiment of this invention, an apparatus tests an ignition coil and a spark plug for defects. The apparatus includes a power supply for supplying power to the ignition coil to generate a spark across the spark plug. A capture circuit captures an energy signal reflected from the ignition coil in response to the spark generation. A comparator circuit compares the captured energy signal to a predetermined signal.
The ignition coil includes a first winding in electrical communication with the power supply and a second winding in electrical communication with the spark plug. Accordingly, the energy signal is reflected from the first winding of the ignition coil in response to the spark generation.
The predetermined signal represents one of a group of distinct reflected energy signals which indicate various defects in an ignition coil or spark plug. In a preferred embodiment, the comparator circuit generates an output in response to a match between the captured energy signal and the predetermined signal to indicate a defective ignition coil or spark plug.
The present invention also provides a method for testing an ignition coil and a spark plug for defects. The method includes the steps of: supplying power to the ignition coil to generate a spark across the spark plug; capturing an energy signal reflected from the ignition coil in response to the spark generation; and comparing the captured energy signal to a predetermined signal. Preferably, the method further includes the step of generating an output in response to a match between the captured energy signal and the predetermined signal to indicate a defective ignition coil or spark plug.
The present invention provides an apparatus and method capable of testing an ignition coil and a spark plug connected in a xe2x80x9ccoil on plugxe2x80x9d design for various types of defects. The present invention is also capable of disclosing which specific type of defect was detected.